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LayerZero Omnichain Contract Examples

• Formal audit(s) (May 21, 2022) can be found in /audit

Install & Run tests

yarn install
npx hardhat test 

• The code in the /contracts folder demonstrates LayerZero behaviours.
• NonblockingLzApp is a great contract to extend. Take a look at how OmniCounter overrides _nonblockingLzReceive and _LzReceive to easily handle messaging. There are also example for OFT and ONFT which illustrate erc20 and erc721 cross chain functionality.
• Always audit your own code and test extensively on testnet before going to mainnet 🙏

The examples below use two chains, however you could substitute any LayerZero supported chain!

OmnichainFungibleToken (OFT)

The OmnichainFungibleToken has two varieties of deployments:

1. BasedOFT.sol - The token supply is minted (on deployment) on the base chain. Other chains deploy with 0 supply initially.
2. OFT.sol - At deploy time, any quantity of tokens can be minted, regardless of chain.

For the BasedOFT, the initial supply will be minted entirely on the Base Chain on deployment. All tokens transferred out of the base chain will be locked in the contract (and minted on destination), and tokens transferred out of other chains will be burned on that chain. Tokens returning to the base chain will be unlocked and transferred to the destination address. This results in the Base chain being like the home base, hence the name.

In the example deployment below we use BasedOFT and the base chain is goerli. This setting is configured in constants/oftBaseChain.json. The OmnichainFungibleToken deployed on other chains will use this configuration to set their base chain. Using the Ethereum network (testnet: goerli) as a base (really its like the source of truth) is a security decision. In the event a chain goes rogue, Ethereum will be the final source of truth for OFT tokens.

About OFTV2

NOTE: the OFTV2 uses uint64 to encode value transfer for compatability of aptos and solana. 

The deployer is expected to set a lower decimal points like 6 or 8. 

If the decimal point is 18, then uint64 can only represent approximately 18 tokens (uint64.max ~= 18 * 10^18).

Deploy Setup

1. Add a .env file (to the root project directory) with your MNEMONIC="" and fund your wallet in order to deploy!
2. Follow any of the tutorials below

BasedOFT.sol - an omnichain ERC20

WARNING: You must perform the setTrustedRemote() (step 2).

1. Deploy two contracts: goerli is the base chain. Fuji is the oft for the other chain.

npx hardhat --network goerli deploy --tags ExampleBasedOFT
npx hardhat --network fuji deploy --tags ExampleOFT

2. Set the "trusted remotes" (ie: your contracts) so each of them can receive messages from one another, and only one another.

npx hardhat --network goerli setTrustedRemote --target-network fuji --local-contract ExampleBasedOFT --remote-contract ExampleOFT
npx hardhat --network fuji setTrustedRemote --target-network goerli --local-contract ExampleOFT --remote-contract ExampleBasedOFT

3. Send tokens from goerli to fuji

npx hardhat --network goerli oftSend --target-network fuji --qty 42 --local-contract ExampleBasedOFT --remote-contract ExampleOFT

Pro-tip: Check the ERC20 transactions tab of the destination chain block explorer and await your tokens!

OmnichainNonFungibleToken721 (ONFT721)

This ONFT contract allows minting of nftIds on separate chains. To ensure two chains can not mint the same nfId each contract on each chain is only allowed to mintnftIds in certain ranges. Check constants/onftArgs.json for the specific test configuration used in this demo.

UniversalONFT.sol

WARNING: You must perform the setTrustedRemote() (step 2).

1. Deploy two contracts:

 npx hardhat --network bsc-testnet deploy --tags ExampleUniversalONFT721
 npx hardhat --network fuji deploy --tags ExampleUniversalONFT721

2. Set the "trusted remotes", so each contract can send & receive messages from one another, and only one another.

npx hardhat --network bsc-testnet setTrustedRemote --target-network fuji --contract ExampleUniversalONFT721
npx hardhat --network fuji setTrustedRemote --target-network bsc-testnet --contract ExampleUniversalONFT721

3. Mint an NFT on each chain!

npx hardhat --network bsc-testnet onftMint --contract ExampleUniversalONFT721
npx hardhat --network fuji onftMint --contract ExampleUniversalONFT721

4. [Optional] Show the token owner(s)

npx hardhat --network bsc-testnet ownerOf --token-id 1 --contract ExampleUniversalONFT721
npx hardhat --network fuji ownerOf --token-id 11 --contract ExampleUniversalONFT721

5. Send ONFT across chains

npx hardhat --network bsc-testnet onftSend --target-network fuji --token-id 1 --contract ExampleUniversalONFT721
npx hardhat --network fuji onftSend --target-network bsc-testnet --token-id 11 --contract ExampleUniversalONFT721 

6. Verify your token no longer exists in your wallet on the source chain & wait for it to reach the destination side.

npx hardhat --network bsc-testnet ownerOf --token-id 1 --contract ExampleUniversalONFT721
npx hardhat --network fuji ownerOf --token-id 1 --contract ExampleUniversalONFT721

OmniCounter.sol

OmniCounter is a simple contract with a counter. You can only remotely increment the counter!

1. Deploy both OmniCounters:

npx hardhat --network bsc-testnet deploy --tags OmniCounter
npx hardhat --network fuji deploy --tags OmniCounter

2. Set the remote addresses, so each contract can receive messages

npx hardhat --network bsc-testnet setTrustedRemote --target-network fuji --contract OmniCounter
npx hardhat --network fuji setTrustedRemote --target-network bsc-testnet --contract OmniCounter

3. Send a cross chain message from bsc-testnet to fuji !

npx hardhat --network bsc-testnet incrementCounter --target-network fuji

Optionally use this command in a separate terminal to watch the counter increment in real-time.

npx hardhat --network fuji ocPoll    

Check your setTrustedRemote's are wired up correctly

Just use our checkWireUpAll task to check if your contracts are wired up correctly. You can use it on the example contracts deployed above.

1. ExampleBasedOFT and ExampleOFT

npx hardhat checkWireUpAll --e testnet --contract ExampleOFT --proxy-contract ExampleBasedOFT --proxy-chain goerli

2. UniversalONFT

npx hardhat checkWireUpAll --e testnet --contract ExampleUniversalONFT721

3. OmniCounter

npx hardhat checkWireUpAll --e testnet --contract OmniCounter

See some examples in /contracts 🙌

Many of the example contracts make use of LayerZeroEndpointMock.sol which is a nice way to test LayerZero locally!

For further reading, and a list of endpoint ids and deployed LayerZero contract addresses please take a look at the Gitbook here: https://layerzero.gitbook.io/

See testnet and mainnet chainIds and addresses, and the format for connecting contracts on different chains:

https://github.com/LayerZero-Labs/set-trusted-remotes https://layerzero.gitbook.io/docs/technical-reference/testnet/testnet-addresses https://layerzero.gitbook.io/docs/technical-reference/mainnet/supported-chain-ids

Most recently tested with node version 16.13.1